Remediation Approaches – In Situ Chemical Oxidation (ISCO), Part 2

When is ISCO a good fit for an environmentally impacted site?

In situ chemical oxidation is not applicable to all contaminants or to all situations. Considerable research has been conducted and is continuing to determine the optimal contaminant–oxidant match.

The application of in situ chemical oxidation is a step-wise procedure involving:

  1. Screening
  2. Bench Scale Testing
  3. Pilot Testing
  4. Design and Permitting
  5. Operation
  6. Closure

The first three of these are explored in more detail below:

Screening

Chemical oxidation is a powerful remediation tool however it is not applicable to all sites or situations. Screening of the appropriateness of chemical oxidation at a specific site generally covers four aspects:

  • Contaminant
  • Geology
  • Site Constraints
  • Regulations

Contaminant

Various contaminant characteristics contribute to the selection of the most appropriate oxidant system: These characteristics include: contaminant type(s), mass, and phase distribution (i.e., dissolved, adsorbed, NAPL), as well as the contaminant’s physical, chemical, and toxicological properties. The interaction between a contaminant and potential oxidant can be Treatability table presented in the previous section rates the potential applicability of each of the four oxidants to a variety of compounds. In many cases the contaminant will respond to several different oxidants. The choice of a particular oxidation system, therefore, must consider a number of factors including reaction time, achievable cleanup levels, cost, ease of application, and regulatory acceptance.

Geology

Site geology determines how easily in situ chemical oxidation can be applied. The key geological parameters considered are lithology, hydrogeology, location of contaminant, depth to water, heterogeneity, and depth to contamination.

Site

The site setting and context affect the decision to use in situ chemical oxidation. Significant factors include current and future receptors, land use, adjacent properties, water bodies, accessibility, liability, value, utility and site constraints, and site construction.

Regulations

Regulatory context often determines the required level of cleanup. It also specifies permit requirements for the application of in situ oxidants.

Laboratory Testing (Bench Scale)

Chemical oxidation is a relatively new remediation technology. To help select the best chemical oxidation system, companies are building a knowledge base comprising the oxidation characteristics of specific contaminants, as well as the responses of specific contaminants in different matrixes.

Laboratory testing is an efficient method of deciding whether in situ chemical oxidation is an appropriate remediation technology for a site. The laboratory testing is used to first determine whether the desired chemical reaction between the oxidant and the contaminant will take place in a reasonable period of time. If the reaction does not occur under optimal conditions, it is unlikely that the reaction will succeed in the field.

Laboratory testing is used to confirm the oxidation of target contaminants, determine the efficiency of oxidant usage, determine the rate of reaction, and assess potential hazards. The laboratory data can aid in the design of field pilot tests and full-scale systems as well as providing supporting data for permitting.

Pilot Testing

When it is known or demonstrated through bench testing, that a particular contaminant can be effectively oxidized, the key design issue becomes delivery. Can the oxidant be supplied in sufficient quantities to the target contaminant treatment areas? Pilot testing is an effective means of answering this question.